This invention relates to power tools and, in particular, to an apparatus for attaching a drive head to the power unit of a tool for driving different accessories, such as nut sockets, fasteners, drill bits, or grinding, sanding, and buffing attachments.
During assembly of complex mechanical systems, it is necessary to use different types of tools for the different fasteners. This situation is dealt with by having an assortment of power tools available which are suitable for any assembly situation. This can be quite expensive, however, and another approach has been to have interchangeable drive heads, as needed, for use on a common power unit. There have been several interchange systems of varying practicality.
One interchange system which requires no separable parts has been in use for a number of years. In this case, the motor housing has splines on its inside diameter which mate with splines on the outside diameter of the drive head. A split clamp ring having a circular cross section is located behind the drive head splines and has a large enough outside diameter to retain a coupling nut. When attaching the head, the coupling nut is threaded to the motor housing. This draws the clamp ring against the splines of the drive head and axially clamps it against the motor housing. This works quite well, but it does have the disadvantages of the cost of machining splines on both housings, of only providing line contact between the clamping members, and of being restricted to angular orientation increments which are dictated by the number of splines and the spline design chosen.
Another interchange system which has been in use by Ingersoll-Rand for several years eliminates the orientation limitations of the previously described system. The drive head housing has a flared end behind which is a coupling nut and a retaining ring having a round cross section. The flare on the drive head has no splines in this case; therefore, this system provides for universal orientation of the drive head with respect to the axis of the motor unit.
Both of the foregoing systems work very well within their limitations. However, both systems share a common shortcoming which is attributable to the round cross section of the retaining ring employed in both cases. When the coupling nut is engaged with the threads on the motor housing and drawn up tight, the retaining ring is trapped between the flare on the drive head and the coupling nut flange. This results in a straight compressive clamping force which is oriented on the diameter of the circular cross section of the ring. This line contact is adequate when the connection is first made; however, during handling of the tool in use, the clamping force decreases and the head becomes loose and requires retightening.
The foregoing limitations present inconvenience associated with routine use of power tools. It would be desirable to provide an alternative attachment method to attach the drive head to the motor housing in such a manner as to avoid the inconvenience and cost of the previously described methods. Accordingly, a suitable alternative is provided which includes features which will be more fully discussed hereinafter.